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fix(dynamixel): correct AX sign-magnitude encoding

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AX-series speed/load are sign-magnitude (direction at bit 10), not two's
complement, and position registers are unsigned. Encode/decode now use
sign-magnitude on Protocol 1 and the AX encoding table stores sign-bit
indices for the speed/load registers only.
This commit is contained in:
CarolinePascal
2026-07-05 17:16:04 +02:00
parent e32974823e
commit 3b7f7cfb22
2 changed files with 24 additions and 10 deletions
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src/lerobot/motors/dynamixel/dynamixel.py
+18 -5
View File
@@ -25,7 +25,12 @@ from typing import TYPE_CHECKING
from lerobot.utils.import_utils import _dynamixel_sdk_available, require_package
from ..encoding_utils import decode_twos_complement, encode_twos_complement
from ..encoding_utils import (
decode_sign_magnitude,
decode_twos_complement,
encode_sign_magnitude,
encode_twos_complement,
)
from ..motors_bus import Motor, MotorCalibration, NameOrID, SerialMotorsBus, Value, get_address
from .tables import (
AVAILABLE_BAUDRATES,
@@ -271,8 +276,12 @@ class DynamixelMotorsBus(SerialMotorsBus):
model = self._id_to_model(id_)
encoding_table = self.model_encoding_table.get(model)
if encoding_table and data_name in encoding_table:
n_bytes = encoding_table[data_name]
ids_values[id_] = encode_twos_complement(ids_values[id_], n_bytes)
param = encoding_table[data_name]
# Protocol 1.0 (AX-series) uses sign-magnitude; Protocol 2.0 (X-series) two's complement.
if self.protocol_version == 1:
ids_values[id_] = encode_sign_magnitude(ids_values[id_], param)
else:
ids_values[id_] = encode_twos_complement(ids_values[id_], param)
return ids_values
@@ -281,8 +290,12 @@ class DynamixelMotorsBus(SerialMotorsBus):
model = self._id_to_model(id_)
encoding_table = self.model_encoding_table.get(model)
if encoding_table and data_name in encoding_table:
n_bytes = encoding_table[data_name]
ids_values[id_] = decode_twos_complement(ids_values[id_], n_bytes)
param = encoding_table[data_name]
# Protocol 1.0 (AX-series) uses sign-magnitude; Protocol 2.0 (X-series) two's complement.
if self.protocol_version == 1:
ids_values[id_] = decode_sign_magnitude(ids_values[id_], param)
else:
ids_values[id_] = decode_twos_complement(ids_values[id_], param)
return ids_values
src/lerobot/motors/dynamixel/tables.py
+6 -5
View File
@@ -166,12 +166,13 @@ X_SERIES_ENCODINGS_TABLE = {
"Present_Velocity": X_SERIES_CONTROL_TABLE["Present_Velocity"][1],
}
# {data_name: size_byte}
# {data_name: sign_bit_index}
# AX-series speed/load use sign-magnitude encoding with the direction stored in bit 10.
# Position registers (0-1023) are unsigned and therefore need no sign handling.
AX_SERIES_ENCODINGS_TABLE = {
"Goal_Position": AX_SERIES_CONTROL_TABLE["Goal_Position"][1],
"Moving_Speed": AX_SERIES_CONTROL_TABLE["Moving_Speed"][1],
"Present_Position": AX_SERIES_CONTROL_TABLE["Present_Position"][1],
"Present_Speed": AX_SERIES_CONTROL_TABLE["Present_Speed"][1],
"Moving_Speed": 10,
"Present_Speed": 10,
"Present_Load": 10,
}
MODEL_ENCODING_TABLE = {